Translation guide
The English word 'vapor' refers to a visible mist, steam, or gaseous substance. In Japanese, the most common equivalent is 蒸気 (じょうき), but other words like 湯気 (ゆげ) for steam from hot water, 水蒸気 (すいじょうき) for water vapor, and 気体 (きたい) for gas are used depending on context. This guide helps learners choose the right term.
To refer to a visible cloud of tiny liquid droplets, such as steam from boiling water, breath on a cold day, or fog.
General term for vapor or steam, often used for industrial or visible steam. Can refer to water vapor or other vapors.
やかんから蒸気が出ている。
Steam is coming out of the kettle.
蒸気機関車
steam locomotive
Specifically steam from hot water or food. Very common in everyday contexts like cooking or bathing.
味噌汁から湯気が立っている。
Steam is rising from the miso soup.
お風呂の湯気で鏡が曇った。
The mirror fogged up from the bath steam.
Scientific term for water vapor, often invisible. Used in weather, physics, or technical contexts.
空気中の水蒸気が凝結して雲になる。
Water vapor in the air condenses to form clouds.
Also used for chemical vapors, like gasoline vapor. Context will clarify.
ガソリンの蒸気に引火した。
The gasoline vapor ignited.
To refer to the gaseous form of a substance that is normally liquid or solid, often in scientific or technical contexts.
General word for gas (state of matter). Use when emphasizing the physical state rather than visibility.
水は液体だが、水蒸気は気体だ。
Water is a liquid, but water vapor is a gas.
Can also mean vapor in the sense of gaseous state, especially when referring to a substance that is normally liquid.
To describe a light mist or fog, often natural or atmospheric.
Fog or mist. Use for natural atmospheric conditions, not for steam from hot water.
朝霧が立ち込めている。
The morning mist is hanging in the air.
Haze or light mist, often implying a thin, lingering vapor. More literary than 霧.
遠くの山が靄にかすんでいる。
The distant mountains are hazy with mist.
To refer to the visible cloud of breath when it's cold.
Literally 'white breath'. The most natural way to describe visible breath in cold air.
寒くて白い息が出る。
It's so cold I can see my breath.
Phrase meaning 'breath is white', used to describe the phenomenon.
外は息が白くなるほど寒い。
It's cold enough outside to see your breath.
蒸気 is a broader term for steam/vapor, including industrial steam, water vapor, and chemical vapors. 湯気 specifically means steam from hot water or food, and is more common in daily life. Use 湯気 for cooking, baths, and hot drinks; use 蒸気 for engines, science, and general vapor.
When talking about visible breath on a cold day, do not use 蒸気. Instead, use 白い息 (しろいいき) or say 息が白い (いきがしろい). Using 蒸気 would sound unnatural and overly technical.
Mercury vapor is toxic.